Light actuated circuits



Filed June 28, 1956 B. G. RAD/N I hINVgNTOR. a Kiw ATTORNEYS ilnitedStates Patent {25915,642 v LIGnrAoTU -rnn-cmcms Claims, (c 4) Thisinvention relates to .light actuated:circuits an d more particularly toa cire uit which,.is;ad ap ted to be used with amotor vehicle headlight{arrangement which automatically changes the intensi ty. -ofthe.headlights upon receiving a signal of light;frornoncoming yehieles.

With this invention it is. possible to have a motor vehicle automaticheadlight dimmingg'assembly by using ,a series of resistances vand onevacuum tube ,with one photoconductive cell. A prin cipleiof thisinvention is-to connect a control grid of the vacuum-tube to ;a.photoconductive cell :which cell ehanges its resistance :upon receivinga light signal thereby changing-thevoltage level of the-grid causingsaidgtubetqconduct. .when the tube iscOnducting, a relay.energizes aswitchyvhich changes a second resistance" in the.gridcireuitgivingthetube a difierent sensitivity .to light so that-afirst increment of light difierential will cause thetubeto-firejbut-a-second and different light differential will-cut ofif .the tube.This is done so that when the;headlights are onahigh beam-a smallincrement .of increased received light will switch them to low butalarge increment of decreased-received light will be necessary to switchthem back to high so that it will .be less likely :that. an..onc .omingdriver :will have a high beamswitched oninto his eyes due tosome smallreduction in light thatrnay be caused ,by a turn or dip intheroadoronecar :turning offin tront :of another. Heretofore, amuch.more complicated system has been necessary to provide the functionsoutline d above. I e e,

Other objectsandadvantagesl of this invention in ,addition to furtherexplanation ofthe above objects will appear in the following detailedde'scriptions of twoembodimentsof this invention:which.Willbebestuhderstood when considered .in connection withthefollowing drawings in which: 1'

Figure '1 is a schematic drawingsh ow i nga circuit for.

one embodiment of this inventi o,n z ind lfigz lre ,2 shows a secondembodiment.ofthisinvention.

Looking at Figure .1 is seenvacuum tubef21 which may be a standardtubewithfthedesignation }1:-2 K5.. as, may be obtained from TungsolhavinganodeZZ, controlgrid- 23, accelerator grid 24, and cathode 25.Photoconductive cell 27 is connected betweenl 'gr'id 23 and switch '28and is of the type which has its resistancelowered upon the reception oflight. Whenswitch is .in its upper position to which it is spring urged,connection is made to resistance 31 and then to plus voltage line 32.When switch 28 i i i owe PQ F ll as i qw uld-b when relay 29 isenergized due to the conducting of tube 21, connection is made toresistance 34' andthen to plus voltage line'32 which .puts .grid.23 at{ahigher'voltage since the drop between resistancea34wand linef32will ofnecessitybe lessthan that between resistance 3 1?an'd line 32 due to thepresence of resistance 33 which is of approximately equal value toresistances 31 and 34. Terminal 37 leads to control beam circuit relay,not shown, which relay is energized to a low beam position when relay 29is energized closing switch 38. Current cut off in tube 21 and-hencerelay 29 willopenlswitch 38, de-energizing the control beam relay,causing the high beam to be actuated.

in the operation of the embodiment shown in Figure -1 light cell 27 .ispositioned to receive the light from oncomingvehicles, and when it sodoes, its resistanceis lowered, raising the potential of grid 23 causingtube -2'1 to conduct. Relay-29 isenergized causingswitches 38'and 28 tochange position. 3 Switch 28 will move downwardly into-thealowbeamposition-while switch 38 will make contact with terminal 37 actuatingthe low beam circuit. Withiswitch 28in thelowenposition the voltage ofgrid 23 is raised a pre-determined amount so'that the resistance .intube 27 -must dr op ria proportionately larger amount to cause tubecutoff and resume the 'high beam position. Thistends to prevent the highbeams from being applied whena slight decrease in light upon tube 27occurs such as might happen when-the oncoming vehicle eithertravelsovera dip inthe road or turns slightly or the oncoming carturns ofi the roadbut is followed by a secondoncoming car.

The components of the circuit shown in Figure :1 may be .as follows.Photo cell 27-.may bean RCA tube-type C7218. .Tube-21 may-be.a'Tungsol12K5 tube. Battery 41 may ,supply 14.4 volts direct currentwhile resistances 42; and 43 may be 100 and27 ohms respectively.:Resistances 31, 33 ,34.may.all be5 kilohms while resistance-44 may be 2.megohms. 1 Resistances 31 and 34 may be varied vto obtain .the'desiredtirnes for tube firing and cutoff. InFigure Zisshown-asecond-circuit for'accomplishing the abovementioned objectives with theadditional iadvantage of eliminating a switch. Battery 51suppliesnapproximately 1.4.4 D.C. volts to the circuit. 'Resistances,.52, 53 maybe respectively and 27,-ohms -and control the voltagesqofaccelerator 54 and cathode 55 in tube 50 .which is in this embodimentealso -a?standard 1 2145. Resistance 58 -=andphoto cell 59 control inpart the-'voltageof grid g56,- and resistance 58 may be =10 kilohmswhiletube v59-is an RCAEtubeC-JQ'IS. Resistance 61is 330-kilohrns whileresistance 62=is variable with a. maximum value of 3--megohms. Relay 63'when'energized switches blade,-64-from an upper or 'high beampositionto the lower or lowbeamposition. Terminal-.65 leads tothe controlvbeamcircuitand whenconnected to switch 64 actuatesthe-low-beam'and whendisconnected the high beam is actuated.

I-n the-position shownswitch 64 is in the high or'upper position andtube 50 is fnot conducting. With switch '64 in the upper-po sitionresistance 62 is by-passed thereby putting the potential of i grid 56 ata lower level than if resistance 62 is in the circuit. When tube 59receives light from an oncoming vehicle its-resistance is loweredraising the voltage ofgrid-56 causing tube 50 to fire. After'tube 50conducts, relay 63.- is energized actuating switch 64 .toa-lowerposition. This activates a'low beam circuit and also putsresistance 62 into the grid circuit further rais- -ing the grid voltageso that a large increment of decreased light'receiv'ed by cell 59,causing a correspondingresistanceincrease, is necessary before tube 50is cut off'bygrid 56.

This'inv'ention may be usedin addition to a manual switchforichangingrfrom high to low beams. An example ofthiskind of circuit isrny copending application filed-June 2'9, 19.53 with Serial 'Number 364,621, now United StatesiPatent 2,763,809. Until the vacuum tube warms:to' operating condition atime delay switch' may be z'usedwto' holdtheiheadlights inlow'beam if. desired. Also, the light sensitivephotoconductive tube may be placed between the control grid and negativevoltage so that light from an oncoming vehicle will cut off the firingof the vacuum tube.

It will be understood that the invention is not to be limited to theexact construction shown and described, but that various changes andmodifications may be made without departing from the spirit and scope ofthe inven tion, as defined in the appended claims.

What is claimed is:

1. In an automatic headlight dimmer for direct operation on a vehiclelow potential electrical power source the combination comprising avacuum tube with a control grid interposed between an anode and acathode, the anode of said vacuum tube being connected to receive apositive potential from the positive terminal of said electrical powersource and the cathode of said vacuum tube being connected to said powersource to receive a lower potential than said anode, a light sensitivevariable resistance having a first and a second terminal and beingconnected at said first terminal to said grid, a first resistance and asecond resistance, said first resistance having a smaller value thansaid second resistance, each of said resistances having one terminalconnected to the positive terminal of the electrical power source andthe other terminal connected to the negative terminal of the electricalpower source, a switching means having a first, a second and a thirdterminal, said first terminal being capable of being selectivelyconnected to either said second terminal or said third terminal, thefirst terminal of said switching means being connected to the secondterminal of said light sensitive variable resistance, the secondterminal of said switching means being connected intermediate the endsof said first resistance, the third terminal of said switching meansbeing connected intermediate the ends of said second resistance forsupplying a higher voltage to the third terminal of said switching meansthan the voltage supplied to said second terminal from said firstresistance, said first terminal of said switch being connected to saidsecond terminal of said switch when said vacuum tube is non-conductingthereby placing a predetermined potential on said control grid, meanspositioned between the anode of said vacuum tube and the positiveterminal of the electrical power source for connecting the firstterminal of the switch to the third terminal of said switch uponconduction of said vacuum tube in response to a given light intensityimpinging upon said light sensitive variable resistance whereby the gridpotential on said control grid is increased above the predetermined gridpotential present when said vacuum tube is in a non-conducting state.

2. In an automatic dimmer for direct operation on a vehicle lowpotential electrical power source the combination comprising a vacuumtube, said vacuum tube including a cathode, an anode and a control grid,the anode of said vacuum tube being connected to receive a positivepotential from the positive terminal of said electrical power source andthe cathode of said vacuum tube being connected to receive a lowerpotential than said anode, a light sensitive variable resistance havingone terminal connected to said grid and the other terminal connected toreceive a positive potential from the positive terminal of saidelectrical power source, means positioned between said grid and saidcathode for biasing said grid to a predetermined potential, a resistorconnected in series with said light sensitive variable resistor andbetween the grid of said vacuum tube and the negative terminal of saidelectrical power source, a relay connected between the anode of saidvacuum tube and the positive terminal of the electrical power sourceadapted to be energized when said vacuum tube conducts, said relayincluding a switch having a first, a second and a third terminal, saidrelay adapted to connect said first terminal of said switch with eithersaid second terminal or said third terminal, the first terminal of saidswitch being connected to the negative terminal of the electrical powersource and to one terminal of said resistor, the second terminal of saidswitch being connected to the other terminal of said resistor with thethird terminal being adapted to actuate an external circuit, the firstterminal of said switch being connected to the second terminal of saidswitch when said vacuum tube is nonconducting thereby shorting out saidresistor, said vacuum tube being rendered conducting by the impingementof light on said light sensitive variable resistance thereby energizingsaid relay and disconnecting the first terminal of said switch from thesecond terminal of said switch and effectively placing said resistor inseries with said light sensitive variable resistance thereby raising thepotential on said grid by the amount of the potential drop across saidresistor.

3. In an automatic dimmer, an electron device having an output circuitand a control circuit, a first voltage source and a second voltagesource for supplying voltages of difierent values, a light sensitivevariable resistance connected in the control circuit of said electrondevice, and means positioned in the output circuit of said electrondevice for connecting the output of the first voltage source to thecontrol circuit when light of a selected intensity impinges upon saidlight sensitive variable resistance and for connecting the output of thesecond voltage source to the control circuit when light of an intensityabove said selected intensity impinges upon said light sensitivevariable resistance.

4. In an automatic headlight dimmer for operation on a power source, anelectron device having an output circuit and a control circuit, a firstvoltage divider and a second voltage divider connected in parallelacross said power source for producing voltages of ditierent values, alight sensitive variable resistance connected in the control circuit ofsaid electron device, and means positioned in the output circuit of saidelectron device for connecting the output of the voltage dividerproducing the lower voltage to the control circuit when light of aselected intensity impinges upon said light sensitive variableresistance and for connecting the output of the voltage dividerproducing the higher voltage to the control circuit when light of anintensity above said selected intensity impinges upon said lightsensitive variable resistance.

5. In an automatic headlight dimmer for operation on a power source, thecombination comprising a vacuum tube having an anode, a cathode and acontrol grid, the anode of said vacuum tube being connected to receive apositive potential from said power source, said cathode being connectedto receive a lower potential from said source than said anode, a firstvoltage divider and a second voltage divider connected in parallelacross said power source for producing voltages of different values, alight sensitive variable resistance connected to the grid of said vacuumtube, and means positioned in the output circuit of said vacuum tubeforconnecting the output of the voltage divider producing the lowervoltage to said light sensitive variable resistance when said tube is ina non-conducting state and for connecting the output of the voltagedivider producing the higher voltage to said light sensitive variableresistance when said vacuum tube is in a conducting state.

References Cited in the file of this patent UNITED STATES PATENTS2,150,900 Alley Mar. 21, 1939 2,476,389 Schmidt July 19, 1949 2,760,114Falge et al. Aug. 21, 1956

